Re: shm_open and EMFILE
Re: shm_open and EMFILE
- Subject: Re: shm_open and EMFILE
- From: David McGavran <email@hidden>
- Date: Sat, 16 Feb 2008 23:28:54 +0100
Like I said asking for help always let you find the answer.
Let me guess XCode sets your limits much higher than running from the
finder? Here are my guess:
Debug in XCode 10240
Run in XCode 2200 something like that
Finder or LSLaunchApplication 253
I never enabled the setrlimit code because when I tested it in the
debugger it wasn't doing anything, because I was already at max.
Is that correct?
Cheers
Dave
On Feb 16, 2008, at 10:40 PM, David McGavran wrote:
Ok, I am officially confused. So hopefully I will solve it as soon
as I write this email ;)
If I launch my app (which is a server) and just loop on creating
files I get 10237 which is cool.
If I launch my app and have a client connect to it using
NSConnection and loop on creating files I get 253, very consistently.
Any ideas why that would be? Are there any debugging tricks for
this? If I look in activity monitor it is showing the 253 files but
not too much else.
Cheers
Dave
On Feb 16, 2008, at 7:17 AM, Terry Lambert wrote:
There are some descriptors used up for normal housekeeping. Also
realize that for ach one you have open, that's a file, socket,
pipe, etc. that you are not going to be able to open.
stdin, stdout, stderr = 3
10237 + 3 = 10240
-- Terry
On Feb 14, 2008, at 11:46 PM, David McGavran wrote:
Ok I guess this is good news then :)
Thanks! I love it when I am wrong :)
I did a much more simple test and was able to hit 10237 which is
much closer to the max of 10240 as I hoped. There must be
something else wrong, I will have to dig deeper.
Cheers
Dave
On Feb 15, 2008, at 2:05 AM, Terry Lambert wrote:
On Feb 14, 2008, at 11:43 AM, David McGavran wrote:
I would guess this has been asked and answered so any pointers
are fine. I tried to check the digest but didn't find the answer.
I am trying to setup a lot of mem mapped files. But at or
around 240 I get EMFILE which man page says means I have too
many open.
If I am not mistaken on 10.5 at least we are allowed 12000 or so
open files? Why can I only open 240 or so memory mapped files?
You are mistaken.
The limit on the number of files for a process is by default 256,
as a soft constraint, and the value of maxfiles, as a hard
constraint. The value of maxfiles represents the maximum number
of files permitted an individual process.
In addition, there is a hard constraint based on whatever your
parent process decides to constrain you to; the default value of
this is "unlimited" (by which it means "whatever the current
sysctl-based hard limits are"). Once lowered the value of the
hard limit cannot be reaised except by a process with root
privilege.
The value of maxfiles is reported by the sysctlbyname() value for
"kern.maxfilesperproc"; this in turn is constrained by the the
sysctlbyname() value for "kern.maxfiles", which is a compile time
system limit.
Note that the use of actual file descriptors to implement POSIX
shared memory is an implementation detail, so all of the above is
potentially subject to change in its relevency if that
implementation detail ever changes.
What can I do to open more?
man 2 setrlimit
Also note that other administrative constraints other than number
of available file descriptors (such as available kernel memory)
will potentially also cause your attempt to ail (e.g. ENOMEM,
ENOSPC, SPERM, EACCES, etc.).
-- Terry
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